Remove FXRC_BITMASK_OUTPUT

FXRC_BITMASK_OUTPUT is only ever set by CFX_AggDeviceDriver when its
bitmap's bits-per-pixel value if 1. However, CFX_AggDeviceDriver's ctor
already verified the bitmap's format never has a bpp of 1.

Change-Id: Ib25675d365c014014e93acfde7adabb805d9da63
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/111771
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fxge/agg/fx_agg_driver.cpp b/core/fxge/agg/fx_agg_driver.cpp
index e1fd404..d197932 100644
--- a/core/fxge/agg/fx_agg_driver.cpp
+++ b/core/fxge/agg/fx_agg_driver.cpp
@@ -1019,10 +1019,8 @@
       if (m_pBitmap->IsAlphaFormat()) {
         flags |= FXRC_ALPHA_OUTPUT;
       } else if (m_pBitmap->IsMaskFormat()) {
-        if (m_pBitmap->GetBPP() == 1)
-          flags |= FXRC_BITMASK_OUTPUT;
-        else
-          flags |= FXRC_BYTEMASK_OUTPUT;
+        CHECK_NE(m_pBitmap->GetBPP(), 1);  // Matches format CHECKs in the ctor.
+        flags |= FXRC_BYTEMASK_OUTPUT;
       }
       return flags;
     }
diff --git a/core/fxge/render_defines.h b/core/fxge/render_defines.h
index 0507e78..055bac3 100644
--- a/core/fxge/render_defines.h
+++ b/core/fxge/render_defines.h
@@ -21,7 +21,6 @@
 #define FXRC_ALPHA_OUTPUT 0x40
 #define FXRC_BLEND_MODE 0x80
 #define FXRC_SOFT_CLIP 0x100
-#define FXRC_BITMASK_OUTPUT 0x400
 #define FXRC_BYTEMASK_OUTPUT 0x800
 #define FXRC_FILLSTROKE_PATH 0x2000
 #define FXRC_SHADING 0x4000